Recovery of the photosynthetic apparatus from photoinhibition during dark incubation of the green alga Dunaliella salina

1999 ◽  
Vol 26 (7) ◽  
pp. 679 ◽  
Author(s):  
Jürgen E. W. Polle ◽  
Anastasios Melis
Keyword(s):  
Reaction Center ◽  
Dunaliella Salina ◽  
De Novo ◽  
Light Harvesting ◽  
Photosynthetic Apparatus ◽  
D1 Protein ◽  
Dark Incubation ◽  
Chl A ◽  
Lag Period ◽  
Stressed Cells

The light-independent recovery of the photosynthetic apparatus from photoinhibition was monitored upon a transition of irradiance-stressed Dunaliella salina Teod. to darkness. Upon dark incubation, the chlorophyll (Chl) a /Chl b ratio of the cells decreased promptly with a half-time of 2.5 h from about 12:1 to about 5:1. In contrast, dark incubation of control cells resulted in only a negligible change of the Chl a /Chl b ratio. During dark incubation of irradiance-stressed cells, the level of the Chl a and b light-harvesting proteins of photosystem II (PSII) increased, a change accompanied by alterations in the composition of these light-harvesting proteins. The amount of photodamaged PSII, measured from the relative amount of a 160 kDa protein complex which contains the photodamaged D1 reaction center protein, decreased during dark incubation after an initial lag period. Concomitantly, the amount of functional PSII, measured from the 32 kDa form of D1, increased slightly in the dark. The results show that, in the dark, photodamaged D1 is slowly removed upon degradation from the thylakoid membrane and replaced by a de novo synthesized D1 protein. The amount of reaction center proteins and number of photochemically active PSI centers increased in the dark. These results suggest that thylakoid membranes of irradiance-stressed D. salina exist in a state of dynamic flux. We conclude that several aspects of the D. salina recovery from photoinhibition are light independent.

scholarly journals The PuhB Protein of Rhodobacter capsulatus Functions in Photosynthetic Reaction Center Assembly with a Secondary Effect on Light-Harvesting Complex 1

2005 ◽  
Vol 187 (4) ◽  
pp. 1334-1343 ◽  
Author(s):  
Muktak Aklujkar ◽  
Roger C. Prince ◽  
J. Thomas Beatty
Keyword(s):  
Reaction Center ◽  
Rhodobacter Capsulatus ◽  
Light Harvesting ◽  
Expression System ◽  
Photosynthetic Apparatus ◽  
Photosynthetic Reaction Center ◽  
Growth Conditions ◽  
Physiological Adaptation ◽  
Light Harvesting Complex ◽  
The Core

ABSTRACT The core of the photosynthetic apparatus of purple photosynthetic bacteria such as Rhodobacter capsulatus consists of a reaction center (RC) intimately associated with light-harvesting complex 1 (LH1) and the PufX polypeptide. The abundance of the RC and LH1 components was previously shown to depend on the product of the puhB gene (formerly known as orf214). We report here that disruption of puhB diminishes RC assembly, with an indirect effect on LH1 assembly, and reduces the amount of PufX. Under semiaerobic growth conditions, the core complex was present at a reduced level in puhB mutants. After transfer of semiaerobically grown cultures to photosynthetic (anaerobic illuminated) conditions, the RC/LH1 complex became only slightly more abundant, and the amount of PufX increased as cells began photosynthetic growth. We discovered that the photosynthetic growth of puhB disruption strains of R. capsulatus starts after a long lag period, which is due to physiological adaptation rather than secondary mutations. Using a hybrid protein expression system, we determined that the three predicted transmembrane segments of PuhB are capable of spanning a cell membrane and that the second transmembrane segment could mediate self-association of PuhB. We discuss the possible function of PuhB as a dimeric RC assembly factor.

scholarly journals Transcriptional Control of Expression of Genes for Photosynthetic Reaction Center and Light-Harvesting Proteins in the Purple BacteriumRhodovulum sulfidophilum

2000 ◽  
Vol 182 (10) ◽  
pp. 2778-2786 ◽  
Author(s):  
Shinji Masuda ◽  
Kenji V. P. Nagashima ◽  
Keizo Shimada ◽  
Katsumi Matsuura
Keyword(s):  
Reaction Center ◽  
Transcriptional Control ◽  
Light Harvesting ◽  
Sequence Similarity ◽  
Blot Hybridization ◽  
Regulatory Region ◽  
Photosynthetic Apparatus ◽  
Northern Blot Hybridization ◽  
Mrna Levels ◽  
Operon Expression

ABSTRACT The purple photosynthetic bacterium Rhodovulum sulfidophilum synthesizes photosynthetic apparatus even under highly aerated conditions in the dark. To understand the oxygen-independent expression of photosynthetic genes, the expression of the puf operon coding for the light-harvesting 1 and reaction center proteins was analyzed. Northern blot hybridization analysis showed that puf mRNA synthesis was not significantly repressed by oxygen in this bacterium. High-resolution 5′ mapping of the puf mRNA transcriptional initiation sites and DNA sequence analysis of the puf upstream regulatory region indicated that there are three possible promoters for thepuf operon expression, two of which have a high degree of sequence similarity with those of Rhodobacter capsulatus, which shows a high level of oxygen repression of photosystem synthesis. Deletion analysis showed that the third promoter is oxygen independent, but the activity of this promoter was not enough to explain the aerobic level of mRNA. The posttranscriptional puf mRNA degradation is not significantly influenced by oxygen in R. sulfidophilum. From these results, we conclude thatpuf operon expression in R. sulfidophilum is weakly repressed by oxygen, perhaps as a result of the following: (i) there are three promoters for puf operon transcription, at least one of which is oxygen independent; (ii) readthrough transcripts which may not be affected by oxygen may be significant in maintaining the puf mRNA levels; and (iii) the puf mRNA is fairly stable even under aerobic conditions.

scholarly journals Structural and Spectroscopic Properties of a Reaction Center Complex from the Chlorosome-Lacking Filamentous Anoxygenic Phototrophic Bacterium Roseiflexus castenholzii

2005 ◽  
Vol 187 (5) ◽  
pp. 1702-1709 ◽  
Author(s):  
Mitsunori Yamada ◽  
Hui Zhang ◽  
Satoshi Hanada ◽  
Kenji V. P. Nagashima ◽  
Keizo Shimada ◽  
...  
Keyword(s):  
Reaction Center ◽  
Phylogenetic Trees ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Photosynthetic Apparatus ◽  
Spectroscopic Properties ◽  
Phototrophic Bacteria ◽  
Amino Acid Sequences ◽  
Anoxygenic Phototrophic Bacteria ◽  
Reading Frame

ABSTRACT The photochemical reaction center (RC) complex of Roseiflexus castenholzii, which belongs to the filamentous anoxygenic phototrophic bacteria (green filamentous bacteria) but lacks chlorosomes, was isolated and characterized. The genes coding for the subunits of the RC and the light-harvesting proteins were also cloned and sequenced. The RC complex was composed of L, M, and cytochrome subunits. The cytochrome subunit showed a molecular mass of approximately 35 kDa, contained hemes c, and functioned as the electron donor to the photo-oxidized special pair of bacteriochlorophylls in the RC. The RC complex appeared to contain three molecules of bacteriochlorophyll and three molecules of bacteriopheophytin, as in the RC preparation from Chloroflexus aurantiacus. Phylogenetic trees based on the deduced amino acid sequences of the RC subunits suggested that R. castenholzii had diverged from C. aurantiacus very early after the divergence of filamentous anoxygenic phototrophic bacteria from purple bacteria. Although R. castenholzii is phylogenetically related to C. aurantiacus, the arrangement of its puf genes, which code for the light-harvesting proteins and the RC subunits, was different from that in C. aurantiacus and similar to that in purple bacteria. The genes are found in the order pufB, -A, -L, -M, and -C, with the pufL and pufM genes forming one continuous open reading frame. Since the photosynthetic apparatus and genes of R. castenholzii have intermediate characteristics between those of purple bacteria and C. aurantiacus, it is likely that they retain many features of the common ancestor of purple bacteria and filamentous anoxygenic phototrophic bacteria.

Macroorganisation and flexibility of thylakoid membranes

2019 ◽  
Vol 476 (20) ◽  
pp. 2981-3018 ◽  
Author(s):  
Petar H. Lambrev ◽  
Parveen Akhtar
Keyword(s):  
Light Harvesting ◽  
Current Knowledge ◽  
Three Dimensional ◽  
Photosynthetic Apparatus ◽  
Dynamic Responses ◽  
State Transitions ◽  
Photochemical Quenching ◽  
Light Harvesting Complex ◽  
Complex Ii ◽  
Light Harvesting Complex Ii

Abstract The light reactions of photosynthesis are hosted and regulated by the chloroplast thylakoid membrane (TM) — the central structural component of the photosynthetic apparatus of plants and algae. The two-dimensional and three-dimensional arrangement of the lipid–protein assemblies, aka macroorganisation, and its dynamic responses to the fluctuating physiological environment, aka flexibility, are the subject of this review. An emphasis is given on the information obtainable by spectroscopic approaches, especially circular dichroism (CD). We briefly summarise the current knowledge of the composition and three-dimensional architecture of the granal TMs in plants and the supramolecular organisation of Photosystem II and light-harvesting complex II therein. We next acquaint the non-specialist reader with the fundamentals of CD spectroscopy, recent advances such as anisotropic CD, and applications for studying the structure and macroorganisation of photosynthetic complexes and membranes. Special attention is given to the structural and functional flexibility of light-harvesting complex II in vitro as revealed by CD and fluorescence spectroscopy. We give an account of the dynamic changes in membrane macroorganisation associated with the light-adaptation of the photosynthetic apparatus and the regulation of the excitation energy flow by state transitions and non-photochemical quenching.

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